The present invention relates to a golf ball composition which is well-suited for use as, in particular, a golf ball cover material. More specifically, the invention relates to a golf ball composition which is capable of greatly improving the durability of the golf ball as a whole while maintaining the initial velocity of the ball.
In recent years, ionomer resins have been widely used in golf ball materials. Ionomer resins are ionic copolymers which are composed of an olefin such as ethylene and an unsaturated carboxylic acid such as acrylic acid, methacrylic acid or maleic acid, and in which the acidic groups are partially neutralized with metal ions such as sodium, lithium, zinc or magnesium. These resins have outstanding qualities in terms of durability, resilience, scuff resistance and the like.
Ionomer resins are currently the predominant type of base resin used in golf ball cover materials. However, because users are constantly on the lookout for golf balls which are endowed with softness and a high rebound, and thus exhibit excellent flight properties, and which also have an excellent durability, various improvements are being carried out on ionomer resins.
Efforts to modify ionomer materials by mixing another thermoplastic resin or thermoplastic elastomer into an ionomer material include, for example, the polymer composition disclosed in JP-B 4-46296, and the method of improving the scuff resistance and cut resistance of game balls having an ionomer cover disclosed in JP-A 10-66740.
In order to provide a cover having a good moldability and excellent resilience, durability and feel, JP-A 2002-331048 discloses a golf ball cover-forming composition which is formulated from an ionomer resin, a thermoplastic urethane material, and a rubbery elastomer composition formulated from, as the essential ingredient, a rubbery elastomer.
In addition, JP-A 2010-51800 describes an ionomer resin composition obtained by compounding a material that is curable by exposure to sunlight, x-rays, ultraviolet light (UV), an electron beam (EB), a plasma arc or the like (UV/EB curable material) together with a thermoplastic resin, in the presence of a peroxide and without carrying out exposure to sunlight, x-rays, ultraviolet light, an electron beam, a plasma arc or the like, then melt-mixing the resulting compound under applied heat with an ionomer resin. This art enables the suppression of layer separation among the golf ball layers, making it possible to obtain a high-performance golf ball having an excellent softness, durability and scuff resistance without a loss of rebound.
However, there exists a desire for golf ball compositions composed primarily of an ionomer resin, which compositions exhibit even further improvements, particularly increased resilience and durability.